Coder matched layer separation for compression of compound documents

Abstract

Methods for decomposing compound documents for mixed raster content representation are provided. A method for decomposing an image includes the step of decomposing the image into a plurality of stripes. Each stripe is decomposed into foreground, background, and mask layers. The layers are interpolated to modify values of irrelevant pixels in order to achieve more efficient compression. The layers may subsequently be compressed with a coder.

Description

FIELD OF THE INVENTION[0001]This invention relates to the field of data compression. In particular, this invention is drawn to representation and compression of compound documents.BACKGROUND OF THE INVENTION[0002]Compound documents may include color images, text, and graphics. Mixed raster content (MRC) is an International Telecommunication Union standard (ITU T.44 04 / 1999) that specifies a method for efficient representation of a compound document as a union of multiple layers. MRC also specifies methods for compressing the document using pre-determined encoders for the individual layers.[0003]Although the ITU T.44 standard sets forth methods for efficient representation of the document once the layers are identified, the standard does not address decomposition of an MRC document into the individual layers. The decomposition approach, however, may have a significant influence on the compressibility of the resulting layers and thus the size of the compressed document. Thus although ...

AI Technical Summary

Benefits of technology

[0006]In one embodiment, a perimeter finding function is used with a common area reduction function to identify a base color for each layer and offsets to common reduced areas thus effectively separating the stripe into foreground and background layers for all regions except where the foreground and background common reduced areas overlap. A coder matched layer separation process is applied to the overlapped common reduced area to separate it into the foreground and background layers before interpolation.

Problems solved by technology

Although the ITU T.44 standard sets forth methods for efficient representation of the document once the layers are identified, the standard does not address decomposition of an MRC document into the individual layers.

The decomposition approach, however, may have a significant influence on the compressibility of the resulting layers and thus the size of the compressed document.

Thus although numerous distinct decompositions of the document may exist, they will not all yield the same level of compression.

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